I wore my Israeli flag yesterday (context). I walked a short ways through downtown Berkeley in public (and went to Jamba Juice), went to a TCS speech by Sarah Fitz-Claridge, and went into two restaurants in Fremont.
Nothing bad happened.
In Berkeley people said something from their car, but I couldn't hear what. They didn't look angry and I waved to them. However it was 9am on Sunday and not many people were around.
At the speech, someone asked why I was wearing a flag. I said that I support Israel, and that if I don't wear a flag no one will ask about it. She didn't say anything so I added that on Saturday Hezbollah was smuggling weapons into Lebanon and Israel sent commandos to stop this, so the UN said Israel broke the cease fire. She thought that was dumb :)